Arrangement, in particular in vehicles, for transmitting electric signals by connecting lines

ABSTRACT

Electric low current signals are transmitted through two-wire circuits having coaxial connectors which are closed by windings that are coupled transformer-like to the coaxial connectors. This arrangement allows transmission of control signals for electric power consuming devices within automobile doors, low frequency audio signals, and electrical power to power the electric consumers. All signals are transmitted on a common data cable. Control signals are in binary coded form, modulated onto a carrier signal, as are modulated, low frequency audio signals. The signals are demodulated in a door module and separated according to frequency. The low frequency audio signals are amplified and transmitted to a loudspeaker. The control signals are processed by a microprocessor controller in conjunction with switching units that create corrective actions for the power consuming devices located in the door.

BACKGROUND OF THE INVENTION

Automobile doors nowadays accommodate quite a number of electric deviceswhich must be supplied with direct current and electric control signals,e.g. window lifters, adjustable exterior mirrors, exterior mirrorheating, hazard light, door lock contacts, contacts for indoor lighting,loud speaker, central lock, possibly also operating unit for an electricsun roof. Using conventional circuitry up to 40 wires are required tocover these needs. This presents, however, a considerable problem whenmounting the doors and renders door repairs more difficult, since thewires must not only be installed, partly in the door and partly in therest of the automobile body, but also in the automobile frame and, bymeans of a flexible cable harness, into the respective door.

Additionally, most wires conduct a load current and must therefore havea sufficiently large cross-sectional area. Considering the fact that thenumber of electric wires in automobiles has strongly increased in thepast years (a modern medium-sized automobile contains approximately1000m cable), automobile manufacturers have in the meantime seriousproblems to accommodate the extensive cable harnesses in the automobile.

Additionally, with increasing number of cables the number of coaxialconnectors required to enable the mounting and dismounting of a doorincreases also. Most of the break downs in the automobile electronicsand electric are due to contact problems of the coaxial connectors ofthe harnesses. Contact problems are facilitated by moisture andaggressive substances penetrating into the coaxial connectors,especially in automobiles. Especially information cables with smallsignal currents are frequently affected, since, unlike in coaxialconnectors conducting load currents, virtually no self cleaning ofcontact surfaces occurs.

The objective of the present invention is to reduce the susceptibilityto break downs brought on by the increasing extend of wiring.

According to the invention electric signals are transmitted by coaxialconnectors with transformer-like coupling. It follows that by doing sonot only are all contact problems in coaxial connectors eliminated, butsimultaneously it becomes possible to drastically reduce the extend ofwiring, since alternating current signal is required for thetransformer-like signal transmission in coaxial connectors and same canbe utilized as carrier signal which can be modulated for not only onebut several different signals to be transmitted to the door.Fundamentally one two-wire circuit only is sufficient to transmit alloccurring signals to the door. For this purpose one part of the coaxialconnector is affixed to the automobile door and the other part of thecoaxial connector to another part of the automobile body. This wayreliable signal transmission is possible into automobile doors which arerotatable supported on hinges, since, if the coaxial connector ismounted on that side of the door which is affixed on the car frame, thenthe two parts of the coaxial connector remain in predetermined, closelyspaced configuration, also during swivel movements of the door,guaranteeing intensive coupling. It is even possible to configure one ofthe door hinges itself as a coaxial connector. For signals which aretransmitted inductively into the door, electric wires between door andautomobile frame are not needed, facilitating wiring significantly andsignificantly improving ease of door repair.

According to the invention not only control signals can be transmittedfor power consuming devices located in the door and their correctiveaction elements, but also low frequency signals from a car radio oranother audio installation in the automobile to a loud speaker locatedin the door. For this purpose the low frequency signals as well ascontrol signals are modulated onto an alternating current carriersignal, which is in turn transmitted inductively in the coaxialconnector and from which control signals and low frequency signals canbe restored through demodulation using an application specific circuitlocated in the door (door module). A particular advantage of theinvention is the fact that not only weak control signals and lowfrequency signals can be transmitted in this way, but also electricpower required for the actuation of power consuming elements, so that nowire connection at all is required between door and automobile frame.The carrier signal can be for the transmission of electric power bychoosing a sufficiently high amplitude to correspond with the requiredpower demand of approximately 50 W; if one takes the carrier signal fromthe demodulator to a rectifier, then the latter can serve as a powersource for the power consuming elements, which also receive the controlsignals.

Several electric power consuming devices are usually located in thedoor, as is the case in mid-size and luxury class automobiles,necessitating that several control signals to be transmitted to thedoor. The control signals are best modulated as a serial data bus ontothe common carrier signal for transmission to the door, where they areseparated according to frequencies into low frequency-, audio- andcontrol signals and then transmitted to their predetermined powerconsuming devices.

Transmitting control signals in the form of a serial data bus is alreadyknown in automotive technology, for example in electronic motor control,but not yet for transmitting control signals into a door. According tothe invention not only a serial data bus is utilized, but same iscombined with coaxial connectors in which low frequency signals,especially audio signals, are transmitted inductively and for thispurpose modulated onto a common carrier. For this purpose a bus controlequipment is required in the automobile and exterior to the door, thatgenerates and transmits the modulated carrier signal, and in the door isrequired an application specific circuit, hereafter named door module,in which the signal is demodulated and separated into control signalsand low frequency signals. The door module supplies the power consumingdevices in the door.

It can occur that a door is equipped with switches and other operatingelements which actuate power consuming devices not located in the samedoor but outside the door or in a different door. Thus, the exteriorrear view mirror on the passenger door can be adjusted and/or thecentral lock can be actuated. It is envisaged that in an advantageousfurther development of the invention control signals, generated in onedoor for electric power consuming devices outside the door, are alsomodulated onto the carrier signal and then inductively transmitted fromthe door to another door module, preferably via a bus control equipmentwhich is connected with all door modules. In this way bi-directionaldata transmission between door modules and the central bus controldevice is possible, bi-directional only for the control signals, ofcourse, but not for the low frequency audio signals, for whichbi-directional transmission is not needed.

There are several possibilities for the selection of the carrier signaland the modulation method. One can use, for example, a sinusoidal orsinusoidal-like alternating current signal, preferably with a frequencybetween 80 kHz and 120 kHz, onto which low frequency signals (frequencyrange approx. 30 Hz to 18 kHz) can be modulated. For the transmission ofbinary coded control signals, one can in this case preferably also usefrequency modulation and one can modulate onto the carrier signal twodiscrete frequencies, preferably above the frequency band used for audiotransmission, representing symbols "0" and "1".

Modems in the form of integrated circuits transmitting signals as serialdata bus according to a carrier frequency method are commerciallyavailable and are suitable for the purpose of the invention.

Another advantageous possibility is the use of a rectangular carriersignal. If a rectangular carrier signal is rectified in the door, adirect voltage is obtained, gap free in the ideal case, which can beutilized, without great effort, for the electric power supply of thepower consuming devices in the door. In this case the carrier signalserves a twofold function: (1) it serves as information carrier and (2)it transmits energy, which is needed by the power consuming devices inthe door in order to function. Thus, a separate cable for energytransmission can be omitted.

The rectangular carrier signal can be frequency modulated or alsoamplitude modulated, but preferably will be pulse-width modulated fortransmission of low frequency audio signals. The maximum modulationneeded for this to work can be obtained, for example, by adjusting thepulse-width-factor between 0.7 and 1.3. Further, when using therectangular carrier signal a frequency of between 80 kHz and 120 kHz forthe carrier signal is preferred. Then the sample frequency isapproximately 10 times the audio frequency (which is low frequency),which is more than sufficient for trouble free low frequencytransmission. The high sample frequency makes a particularly simplemodulation and demodulation possible.

In case of a rectangular carrier signal the binary coded control signalsare preferably superimposed on the carrier signal by amplitudemodulation. For this purpose the rectangular voltage pattern of thecarrier signal is used during one period as a "blank frame" for a bit tobe transmitted of a series of bits. Thus, as will be described below,coding of four different states in every transmission period is easilyachieved. The two parts of the inductive coaxial connector, by means ofwhich the signals are transmitted into the door, are preferablyconfigured similar to a hinge or form a door hinge, which, as a thirddoor hinge, is situated between the two load bearing door hinges,preferably, however, replaces one of the load bearing door hinges, andthus has not only a load bearing but also an inductive transmissionfunction. This version of the invention is particularly economic andeasy to mount.

A coaxial connector configured as a hinge is, for all practicalpurposes, a transformer whose primary winding is affixed to theautomobile frame and whose secondary winding is affixed to the door,enclosing its ferromagnetic hinge pin, which is projected into aferromagnetic yoke affixed to the frame and which closes the magneticwinding between primary winding and secondary winding. In order for thehinge pin to serve not only its magnetic task but also its load bearingmechanical task as a hinge pin, it consists of a longitudinally slottedtube made from non-magnetic steel, e.g. from V2A, and contains a softmagnetic core. It is another possibility to form the hinge pin from ametal band with low losses made from an amorphous material. The yokebest consists of a ferrite but can also consist of an amorphousmaterial.

The invention is not limited to transmitting signals into an automobiledoor, but can be applied whenever low current signals are sent from atransmitter by means of a two-wire circuit to a receiver and a coaxialconnector is provided which can have contact problems. The transmittercan be, e.g. a control device, a signal emitter or a switching devicewhich switches an electric power source. The receiver can be anarbitrary electric power consumer, e.g. a control motor or anothercontrol device, a signal emitter, a loud speaker, a switching device ora controllable sensor.

In all these cases signals can be transmitted from transmitter toreceiver via two-wire circuits which are closed by windings and coupledby transformer-like coupling, but not through direct contact betweenelectric contact pairs. Besides the application in automobiles theinvention can also be applied in construction machinery, land and airvehicles. Stationary possibilities of deployment are given in household,process and machine control technology.

Care is to be given to providing sufficient inductive coupling betweenwindings which close the two-wire circuits to be connected. This isaccomplished by connecting the two winding, as already known, with amagnetic flux conductor made from ferromagnetic material, especiallyferrite, in that the two windings are assembled on a ferrite core.Preferably the coaxial connector contains a divided magnetic fluxconductor, with one part situated in one part of the coaxial connectorwith at least one winding, and the other part of the magnetic fluxconductor situated in the other part of the coaxial connector with atleast one winding, whereby the two parts of the magnetic flux conductorcombine into one core, preferably with magnetic closure on the outsideof the winding.

It is an essential advantage of the invention that both parts of thecoaxial connector can be configured equally.

Changing the orientation of the winding on the core changes the signalpolarity. This may be advantageous in certain applications. In thosecases were the signal polarity is predetermined, the shape of the fluxconductor, the winding and the winding body are designed such that thewinding can be passed over the magnetic flux conductor in oneorientation only.

Using the coaxial connector, according to the invention, not only twobut more than two two-wire circuits can be connected with each other, byconfiguring the coaxial connector such that on the flux connector in oneand/or the other part of the coaxial connector not only one each but twoeach or more than two each windings can be assembled. Thus one can buildvery simple branches, but also redundant signal wire systems, thelatter, for example, as follows: two two-wire circuits, each having awinding on either end and the two windings on one end of each circuitare engaged on one common core, and the other two windings on theopposite end of each circuit are engaged on a second common core.

The required inductive coupling between the two coaxial connector partsaccording to the invention does not necessarily require that the twomagnetic flux conductor parts, one inside each of the two coaxialconnector parts, make contact with each other when the two coaxialconnector parts are joined together, but there may be a gap between thetwo causing losses. The gap does not have to be an air gap, but it maybe filled with a non-magnetic, electrically insulating material, e.g. aplastic material. This is realized in a configuration of the coaxialconnector where the two parts are not penetrating into each other and/orare not transmitting any forces to each other, e.g., a design where eachof the two parts has a plane surface which face each other when the twoparts are strapped together. We consider such a configuration a coaxialconnector also. The outer strap could be, e.g. a shrinkable plasticwhich would not only keep the two parts of the coaxial connectortogether, but would also seal them against penetration of dust andmoisture. Application examples are shown on attached sketches. Identicalor corresponding parts are shown with the same reference numbers.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a circuit for energy transmission by meansof a carrier signal;

FIG. 2 shows, as detail to block diagram of FIG. 1, a circuit for energytransmission by means of the carrier signal;

FIG. 3 shows corresponding voltage as function of time of a rectangularcarrier signal on the primary winding of a transformer;

FIG. 4 shows the current as function of time of the carrier signal;

FIG. 5 shows the corresponding voltage as function of time of thecarrier signal on the secondary winding of the transformer;

FIG. 6 shows direct voltage, gained through rectifying the carriersignal shown in FIG. 5, for the supply of electric power consumers inthe door;

FIG. 7 shows, as detail to block diagram shown in FIG. 1, a circuitry inblock diagram representation for the transmission of a low frequencyaudio signal;

FIG. 8 shows a low frequency audio signal as a function of time;

FIG. 9 shows a saw tooth voltage with which the low frequency audiosignal shown in FIG. 8 is scanned;

FIG. 10 shows the pulse-width modulated rectangular signal on theprimary winding of the transformer gained from scanning the lowfrequency audio signal;

FIG. 11 shows the corresponding pulse-width modulated rectangular signalon the secondary winding of the transformer;

FIG. 12 shows a sequence of direct current pulses which are obtainedthrough circuit shown in FIG. 14 and whose amplitude reflects the pulseduty factor of the rectangular signal shown in FIG. 11;

FIG. 13 shows the low frequency audio signal which was restored fromsignal shown in FIG. 12 by low pass filtering;

FIG. 14 shows as detail to FIG. 1 a circuit which receives and processesthe pulse-width modulated signals shown in FIG. 10;

FIG. 15 shows a carrier signal modulated for transmission of binarycoded control signals;

FIG. 16 shows as detail to FIG. 1 a circuit for the transmission ofbinary coded control signals;

FIG. 17 shows in plan view the parts of an inductive coaxial connectorconfigured as a door hinge;

FIG. 18 shows the elements of the coaxial connector from FIG. 17 in sideview, partly in cross-section;

FIG. 19 shows schematically a transmission installation with inductivecoaxial connectors for other applications;

FIG. 20 shows a transmission system with inductive coaxial connectorallowing branching;

FIG. 21 shows a transmission system with inductive coaxial connectorsand redundant cables; and

FIG. 22 shows a transmission installation with an inductive coaxialconnector whose two parts have plane faces that are facing each otherwhen joined together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The circuit in FIG. 1 contains a bus control equipment 1, which islocated in the vehicle exterior to the doors, e.g. behind the dashboard, and a door module 2 in the left door and a door module 3 in theright door. Both doors contain loud speakers 4 and 5, respective andcorrective action devices 6 and 7, for different power consumers,especially for adjusting the exterior mirrors, for window lifters andfor the central lock. Moreover, each door is equipped with variousrespective operating elements 8 and 9.

The bus control equipment 1 contains an inquiry unit 10 forinterrogating switch positions and other operating elements 16 locatedexterior to doors, a circuit 11 connected with car radio 17 for feedingin low frequency signals coming from two channels (right and left stereochannel), a frequency generator 12 for generating an alternating voltagecarrier signal with a frequency of approximately 100 kHz, amodulator/demodulator 13 (modem), a microprocessor 14 controlling thesequence of operations in the bus control equipment and a circuit 15 forthe exchange of information between bus control equipment 1 and acentral locking mechanism 18 and an alarm installation 19.

The door modules also contain an inquiry unit 20 and 30, resp., forinterrogating the switch positions and other operating elements in therespective door, a modulator/demodulator 21 and 31, a low frequencyamplifier 22 and 32, switching units 23 and 33, for convertingdemodulated control signals into corrective action signals forcorrective action devices 6 and 7, of electric power consuming devices,located in the respective door, a micro controller 24 and 34, whichcontrols the actions in door module 20 and 30, and a rectifier 25 and35, resp., in order to produce a direct current through rectifying thecarrier signal for supplying energy to the electric power consumingdevices.

The bus control equipment 1 is connected to a power source (vehiclebattery) by means of a ground wire 40 and a voltage carrying wire 41. Adata wire pair 42, connected to data port D1 of bus control equipment 1,leads to the left door through a coupler 44, and a data wire pair 43,connected to data port Dr, leads to the right door through a coupler 45.

Couplers 44 and 45 are coaxial connectors configured as door hinges andare constructed as shown in FIGS. 14 and 18. One half of the door hinge50 has a fork shaped sheet metal base plate 51 with poor magnetic fluxcapability, e.g. made from V2A steel, and is connected to the car frame.Affixed to each of the two extensions 52 and 53 of base plate 51 is ayoke 54, made from a ferromagnetic material, e.g. from a ferrite or anamorphous metal. The yokes are connected with each other in their oneend by a cylindrical ferromagnetic core 55 which has an electric winding56 on it. Each extension 52 and 53 is bent into a hook 57 which isdimensioned to house the other end of yoke 54 which, in turn, contains atransverse round hole 58 to suit hinge pin 59 which preferably consistsof a tube, slotted longitudinally, and is made from a non-magneticmaterial (e.g. V2A steel) with a soft magnetic core which simultaneouslyserves as core for another electric winding 66 which is situated in thesecond half 60 of the hinge. The second half of the hinge consists of asheet metal base plate 61 with poor magnetic flux capability and isaffixed to the door. The sheet metal base plate 61 is bent into analmost closed cylindrical bushing 62 which contains winding 66. In orderto shield winding 66 somewhat from mechanical forces transferred fromhinge pin 59, steel bearings 63 and 64 are provided at both ends of thewinding 66 which, together with winding 66, form one unit and, in orderto avoid a short circuit winding, are slotted longitudinally.

When mounting the door, one half 60 of hinge is inserted into thefork-like hinge part 50, so that round hole 65 in winding 66 is alignedwith round hole 58 in yoke 54 whereupon pin 59 is inserted into holes 58and 65 connecting the two halves of the hinge together. Pin 59 transmitsmechanical forces mostly to bearings 63 and 64. After the door ismounted the two windings 56 and 66 are coupled by a magnetic circuitconsisting of the two yokes 54, the core 55 and pin 59 together forminga transformer with primary winding 56 and secondary winding 66.

The circuit works as follows:

Inquiry unit 10 contained in bus control equipment 1 cyclicallyinterrogates operating elements 16 assigned to it; binary coded controlsignals, containing the positions of interrogated operating elements,are being modulated by modem 13 onto the carrier signal which issupplied by frequency generator 12, and, depending on the codeddestination, transmitted either into the right door or into the leftdoor or into both doors. If car radio 17 is switched on, then the lowfrequency signals coming from the car radio and to be sent to door loudspeakers 4 and 5 are fed into the bus control equipment 1 and are alsomodulated onto the carrier signal by modem 13, whereby, in the case ofstereo signals, the left channel is transmitted by means of data wirepair 42 to door module 2, and the right channel by means of data wirepair 43 to door module 3. In case of mono low frequency signals, thesame low frequency signals are being transmitted through data wire pairs42 and 43.

Signals arriving in door modules are demodulated in modems 21 and 31,and separated according to frequency. The low frequency signals areamplified through low frequency amplifiers 22 and 32, and transmitted todoor loud speakers 4 and 5, The demodulated control signals areevaluated by micro-controller 24 and 34, and control the variouscorrective action elements 6 and 7, by means of switching units 23 and33. The carrier signal after rectified in rectifier 25 and 35, suppliesdirect current for the operation of the power consuming devices in thedoor. The inquiry units 20 and 30 in the two door modules 2 and 3,cyclically interrogate the position of operating elements 8 and 9,located in the same door and supply binary coded control signalscontaining the positions of the interrogated operating elements. Themicro controller 24 and 34, checks whether the interrogated operatingelement belongs to a corrective action element in the same door or to acorrective action element outside the door.

If it belongs to a corrective action element in the same door, then thecorrective action element is controlled directly by the correspondingcontroller, without going back to bus-control equipment 1, throughswitching unit 23 and 33. If for example, the interrogated operatingelement 8 in the left door belongs to a corrective action element 7 inthe right door, then the binary coded control signal, delivered byinquiry unit 20, is modulated in modem 21 onto the carrier signal,transmitted to bus control equipment 1, demodulated there, evaluated,again modulated onto the carrier signal and transmitted into the rightdoor, demodulated there in modem 31 and then actuates corrective actiondevice 7 via switching unit 33.

Bus control equipment 1 can furthermore receive signals from, e.g. thetrunk lock which is a part of the central lock 18, and pass them on tothe two door modules 2 and 3. Furthermore signals can be transmitted viabus control equipment to an alarm installation 19 and back from thealarm installation to door modules 2 and 3.

As to the carrier signal, preferably a high frequency rectangularalternating voltage signal is utilized, as depicted in FIG. 3. Such acarrier signal can be easily generated from the voltage of a batterylocated in the car by a bridge circuit 46 depicted in FIG. 2. Four fastelectronic switches S1, S2, S3 and S4 are connected together to form abridge 46 which is powered through wires 40 and 41 from the vehiclebattery. Either switches S1 and S2, or switches S3 and S4 are closed,and this setting alternates so that the rectangular voltage depicted inFIG. 3 appears at the contacts of coaxial connector 44 which is atransformer. By virtue of the rectangular form of the alternatingvoltage signal, a constant voltage is generated at the primary winding56 of the transformer, in the ideal case creating a linearly increasingcurrent (FIG. 4) and producing a constant flux change in core 55, 59.The constant flux change creates a constant secondary voltage (FIG. 5).By continuously changing the polarity of the primary voltage Utp (FIG.3) a triangular current in time (FIG. 4) and a secondary rectangularalternating voltage Uts (FIG. 5) is generated, which is rectified indoor module 2 (or 3) by a rectifier bridge 47 consisting of diodes D1 toD4, resulting in a direct voltage shown in FIG. 6, which is gap free inthe ideal case. The extent of smoothing of this direct voltage islimited to bridging the needle shaped voltage breakdowns caused by thefinite slope of the pulse edge. The current flux angle and through itthe transformer efficiency is much better than for a sinusoidal primaryvoltage. Rectifier bridge 47 serves as a power source for electric powersupply to power consuming devices in the door.

The transmission of a low frequency signal can be achieved throughmodulation of the pulse duty factor of the rectangular carrier signaldepicted in FIG. 3 which, for this purpose, preferably has a frequencyof 100 kHz, as an order of magnitude. The circuit shown in FIG. 7illustrates this point further. The low frequency signal is passedthrough a low pass filter 71, thereby limiting its band width andamplitude, and a constant direct voltage Uo is added for the purpose ofsetting a suitable working point. The resulting low frequency directvoltage signal Unf is shown in FIG. 8. Between low pass filter 71 andbridge circuit 46 (see FIG. 2), control circuit 72 is placed. The lattercontrols the setting of switches S1 and S2, and S3 and S4, resp.,contained in bridge circuit 46. A timing generator 73 provides a 100 kHztiming signal. For example, at one particular time switches S1 and S2are closed and switches S3 and S4 are open; the rate at which saidswitches change their setting is 100 kHz. The exact point in time withinone period of the timing generator at which switches S1 and S2, and S3and S4, are actuated is determined through scanning of signal shown inFIG. 8 by saw tooth voltage Usgz shown in FIG. 9. The latter isgenerated by timing generator 73 which, has an amplitude of 2Uo with nopolarity change, and a 100 kHz frequency. The saw tooth voltage Usgz iscompared with the low frequency voltage Unf in control circuit 72.

The comparison begins with each period of the timing generator 73; assoon as the saw tooth voltage reaches the actual voltage Unf, bridgecircuit 46 changes polarity; when the new period of the timing generatorbegins bridge circuit 46 again changes polarity. Thus, the magnitude ofamplitude Unf is coded into the pulse duty factor.

The pulse width modulated signal is transmitted into the door throughcoupling 44 which is configured as a transformer. The circuit of doormodule 2 inside the door is shown in FIG. 14 and comprises bridgecircuit 47 (see FIG. 2), a circuit 74 for converting the pulse dutyfactor, a low pass filter 75, a low frequency amplifier 22 and aphase-locked control circuit 76. The pulse duty factor converter 74determines the sign of the pulse-width modulated rectangular voltageand, when voltage is negative, switches a power source from bridgecircuit 47 to the pulse duty factor converter to a capacitor C, which isthen being charged for as long as the negative portion of therectangular voltage (FIG. 11) persists; concurrently the voltage in thecapacitor C increases linearly (FIG. 12) then remains constant untilcapacitor C is discharged at the beginning of each 100 kHz cycle by anelectronic switch 77. The phase-locked control circuit is locked ontothe working frequency of 100 kHz of the system and transmits to thepulse duty factor converter 74 the required control signals, by whichcapacitor C is discharged at the beginning of each 100 kHz cycle. Thevoltage as function of time on capacitor C is shown in FIG. 12 andrepresents a sequence of impulses whose amplitude is determined by thepulse duty factor of the pulse-width modulated rectangular voltage inFIG. 10 and 11. The voltage Uc on capacitor C is composed of the lowfrequency signals, the system frequency of 100 kHz, upper harmonics ofthe system frequency and a direct voltage portion; it is sent to anAC-coupled low pass filter of higher order 75, which separates out thelow frequency content and passes same to the low frequency amplifier 22,which finally feeds the loud speaker. The low frequency amplifier 22 issupplied with power by bridge circuit 47 also. The low frequency signalsent to low frequency amplifier 22 is shown in FIG. 13.

Commands and status information is transmitted in the form of a sequenceof binary coded signals (data telegram). For this purpose the period ofthe carrier signal Ut (see FIG. 3) is used as a "blank frame" for a bitof the serial data telegram to be transmitted. If this "blank frame" ismarked after every status change, then it is possible to code fourstatuses in every transmission period--as shown in FIG. 15:

    ______________________________________                                        1. marking 1                                                                            not present,                                                                              marking 2   not present                                 2. marking 1                                                                            present,    marking 2   not present                                 3. marking 1                                                                            not present,                                                                              marking 2   present                                     4. marking 1                                                                            present,    marking 2   present                                     ______________________________________                                    

In order to increase transmission reliability the given code range canbe used redundantly:

    ______________________________________                                        No transmission:                                                              1. marking 1                                                                            not present,                                                                              marking 2   not present                                 Logic "1":                                                                    2. marking 1                                                                            present,    marking 2   not present                                 Logic "0":                                                                    3. marking 1                                                                            not present,                                                                              marking 2   present                                     Start-Stop-Bit:                                                               4. marking 1                                                                            present,    marking 2   present                                     ______________________________________                                    

Such markings can be superimposed on the rectangular impulses in modem13 (FIG. 1) in the form of a high frequency signal with a frequency ofseveral MHz (high frequency burst) and modem 21 and 31, in door module 2and 3, restores the transmitted data telegram. For the transmission ofthe data telegram one can utilize the circuit depicted in FIG. 16 wherethe coaxial connector is configured as a transformer and apart from theprimary main winding 56 and the secondary main winding 66, hasadditionally on the same core a primary supporting winding 56a and asecondary supporting winding 66a. The supporting windings 56a, 66a canbe connected, by means of a switch 81 and 82, with a RC combination 83,84 to form a damped oscillating circuit. Moreover, each supportingwinding 56a, 66a is equipped with an oscillation detector 85, 86. If apulse edge is to be marked in the manner shown in FIG. 15, then theoscillating circuit is closed on the transmitter side and excited todamped oscillations in the transformer by the pulse edge. Thisoscillation is transmitted to the opposite side of the transformer andis passed on to the oscillation detector 85 and 86, via the openwinding, from which the data telegram can be restored from the outputsignal.

FIG. 19 shows a transmission installation with modem 91, e.g. aFSK-modem, as a transmitter. Modem 91 transmits signals, modulated ontoa carrier signal, to a receiver which is not shown. The signaltransmission is accomplished by means of twisted two-wire circuits 93,which are coupled to each other by means of an inductive coaxialconnector. A first two-wire circuit 93 is connected to modem 91 and isclosed on the other end by a winding located in the coaxial connector44. Two more twisted two-wire circuits 93 are connected to coaxialconnector 44 and each is closed on either end by a winding. Two oftheses windings are positioned in the coaxial connector 44 and the othertwo windings 90, located outside the coaxial connector 44, can be partof other similar coaxial connectors.

Essential elements contained in the coaxial connector, represented onlyschematically, are the three windings 90, two ferrite shells 92 withcylindrical core 95 and cylindrical housing 96. When the two parts 44aand 44b are joined together, the two half shells 92 form an essentiallyclosed hollow cylindrical flux conductor with a core 95. By virtue ofthe fact that one two-wire circuit leads into and two two-wire circuitsexit from the coaxial connector, branched cable systems can beconstructed. An example, shown in FIG. 20, shows an inductive coaxialconnector, whose ferrite core 95 is equipped with three windings 90. Afirst two-wire circuit leads to a first module 97 where it connects toan inductive coaxial connector 144, similar to coaxial connector 44,whereby a part of coaxial connector 144, similar to an equipment jack,is part of module 97 and the other part of coaxial connector 144 isconnected to the end of two-wire circuit 93. Correspondingly, a secondtwo-wire circuit 93, extending from coaxial connector 44, leads to asecond module 98 which, in turn, may be connected to sensors andactuators. In the second module 98 further branching takes place bymeans of a two-wire circuit 93 connected to coaxial connector 144 andleading to another module or equipment 99. Finally, a third two-wirecircuit connected to coaxial connector 44 leads to a fourth module orequipment 100.

Branching as demonstrated in module 98 is also possible in module 97.

FIG. 21 shows a redundant cable connection between two modules 97 and 98which are connected with each other, by means of two coaxial connectors144 each having two ports and two parallel two-wire circuits 93. If onesignal path through one of the two-wire circuits 93 is blocked, then theother signal path via the other two-wire circuit is still available fortransmission.

FIG. 22 shows a connector composed of two identical parts each of whichcontains a modem 91 connected by means of a twisted two-wire circuit 93to a winding 90 which is embedded inside a cylindrical magnetic fluxconductor 92, open on one side, with a core 95. The open ends of the twomagnetic flux conductors 92 face each other, and are closely positionedbehind the plane housing surfaces 101 and 102. When the two housingsurfaces 101 and 102 are in full contact with each other, then the twoflux conductors 92 are separated by a layer of plastic, the buildingmaterial of the housing, through which magnetic flux can penetrate. Thetwo parts 44a and 44b of the connector are held together by an outerdevice, e.g. by a clamp or shrink sleeve, as indicated by double arrow103.

Utilizing the transmission installations shown in FIGS. 19 to 22,daisy-chain bus structures for the serial transmission of data can beconstructed. The topological system arrangement can correspond to allknown serial bus systems. The information can be transmitted using anymethod based on the modulation of the carrier frequency, i.e. carrierfrequency method, for example, the FSK method(Frequenz-Shift-Kodierung). The transmission of data telegrams can occurin both directions; when using the FSK method, however, not at the sametime (half-duplex). Using other carrier frequency methods a full duplexmethod can be realized. A particular advantage is the fact that branches(bus nodes, FIG. 20) and redundant bus systems (FIG. 21) can be realizedwith ease, as long as the two bus branches do not exhibit significantsignal phase shift.

We claim:
 1. An apparatus for the transmission of low current electricsignals through cables of a vehicle from a transmitter to a receiver bymeans of two-wire circuits which said circuits contain at least onecoaxial connector for separating said transmitter from said receiver,said two-wire circuits closed by transformer-like windings coupled inthe coaxial connector, wherein the two wires of the two-wire circuit aretwisted into each other.
 2. An apparatus for the transmission of lowcurrent electric signals through cables of a vehicle from a transmitterto a receiver by means of two-wire circuits, which said circuits containat least one coaxial connector for separating said transmitter from saidreceiver, said transmitter including a frequency generator forgenerating a carrier signal, a modulator for modulating signals onto thecarrier signal, said signals to be transmitted to the receiver, saidreceiver including a demodulator for restoring signals by demodulation,wherein said carrier signal is a rectangular one.
 3. An apparatus forthe transmission of low current electric signals through cables of avehicle from a transmitter to a receiver by means of two-wire circuits,which said circuits contain at least one coaxial connector forseparating said transmitter from said receiver, said transmitterincluding a frequency generator for generating a carrier signal, amodulator for modulating signals onto the carrier signal, said signalsto be transmitted to the receiver, said receiver including a demodulatorfor restoring signals by demodulation, wherein the modulator is afrequency modulator.
 4. An apparatus for the transmission of low currentelectric signals through cables of a vehicle from a transmitter to areceiver by means of two-wire circuits, which said circuits contain atleast one coaxial connector for separating said transmitter from saidreceiver, said transmitter including a frequency generator forgenerating a carrier signal, a modulator for modulating signals onto thecarrier signal, said signals to be transmitted to the receiver, saidreceiver including a demodulator for restoring signals by demodulation,wherein the modulator is a pulse-width modulator in order to transmitlow frequency audio signals.
 5. An apparatus for the transmission of lowcurrent electric signals through cables of a vehicle from a transmitterto a receiver by means of two-wire circuits, which said circuits containat least one coaxial connector for separating said transmitter from saidreceiver, said transmitter including a frequency generator forgenerating a carrier signal, a modulator for modulating signals onto thecarrier signal, said signals to be transmitted to the receiver, saidreceiver including a demodulator for restoring signals by demodulation,wherein the receiver further includes a rectifier as a power source forthe supply of the receiver which rectifies the carrier signal. 6.Apparatus as set forth in claim 5 in which, signals are binary coded andtransmitted on the carrier signal as a serial data form.
 7. An apparatusfor the transmission of low current electric signals through cables of avehicle from a transmitter to a receiver by means of two-wire circuits,which said circuits contain at least one coaxial connector forseparating said transmitter from said receiver, said transmitterincluding a frequency generator for generating a carrier signal, amodulator for modulating signals onto the carrier signal, said signalsto be transmitted to the receiver, said receiver including a demodulatorfor restoring signals by demodulation, wherein said signals are binarycoded and transmitted on the carrier signal in serial data form, whereinan amplitude modulator is provided which modulates the binary signalsonto the carrier signal through amplitude modulation.
 8. The apparatusas set forth in claim 7, wherein the amplitude modulator is one of animpulse generator and a frequency generator whose output signal is addedto the carrier signal.
 9. An apparatus for the transmission of lowcurrent electric signals through cables of a vehicle from a transmitterto a receiver by means of two-wire circuits, which said circuits containat least one coaxial connector for separating said transmitter from saidreceiver, said transmitter including a frequency generator forgenerating a carrier signal, a modulator for modulating signals onto thecarrier signal, said signals to be transmitted to the receiver, saidreceiver including a demodulator for restoring signals by demodulation,in which modems are provided serving as the modulator as well as thedemodulator enabling carrier signal transmission in both directions. 10.An apparatus for the transmission of low current electric signalsthrough cables of a vehicle from a transmitter to a receiver by means oftwo-wire circuits, which said circuits contain at least one coaxialconnector for separating said transmitter from said receiver, saidtransmitter including a frequency generator for generating a carriersignal, a modulator for modulating signals onto the carrier signal, saidsignals to be transmitted to the receiver, said receiver including ademodulator for restoring signals by demodulation, wherein low frequencyaudio signals, for a loud speaker are also modulated onto the carriersignal, and are separated from other signals according to frequency atthe receiver, and amplified, and sent to the targeted receiver, such asa loud speaker.
 11. An apparatus for the transmission of low currentelectric signals through cables of a vehicle from a transmitter to areceiver by means of two-wire circuits, which said circuits contain atleast one coaxial connector for separating said transmitter from saidreceiver, said transmitter including a frequency generator forgenerating a carrier signal, a modulator for modulating signals onto thecarrier signal, said signals to be transmitted to the receiver, saidreceiver including a demodulator for restoring signals by demodulation,wherein a frequency between 80 kHz and 120 kHz is chosen as a frequencyof the carrier signal.
 12. An apparatus for the transmission of lowcurrent electric signals through cables of a vehicle from a transmitterto a receiver located within said vehicle by means of two-wire circuits,which said circuits contain at least one coaxial connector forseparating said transmitter from said receiver, said two-wire circuitsclosed by transformer-like windings coupled in the coaxial connector,wherein said transmitter includes a frequency generator for generating acarrier signal, and a modulator for modulating signals onto the carriersignal, said signals to be transmitted to the receiver, said receiverincluding a demodulator for restoring signals by demodulation, whereinsaid modulator modulates electric signals for a plurality of receiversonto said same carrier signal, wherein the receivers are located in adoor of said automobile, the transmitter is located elsewhere in theautomobile and, in the area where the door is rotatably affixed to theautomobile frame with hinges, one part of the coaxial connector isaffixed to the door and another part of the coaxial connector is affixedto the automobile body.
 13. The apparatus as set forth in claim 12,wherein a bus control equipment is provided for the supply of severalelectric power consuming devices in the door with electric controlsignals and for the supply of another power consuming device, such as aloud speaker with low frequency audio signals, and that the bus controlequipment contains an inquiry unit for interrogating the position of oneof the switches and operating elements located exterior to the door anda microprocessor for controlling the sequence of operations in the buscontrol equipment, whereby the modulator receives the low frequencysignals and modulates them onto the carrier signal and receives controlsignals from the inquiry unit and modulates them onto the carrier signalin serial data form, and that the demodulator located in the doorreceives signals from the bus control equipment, demodulates them andseparates them into control signals and low frequency signals.
 14. Anapparatus for the transmission of low current electric signals throughcables of a vehicle from a transmitter to a receiver located within saidvehicle by means of two-wire circuits, which said circuits contain atleast one coaxial connector for separating said transmitter from saidreceiver, said two-wire circuits closed by transformer-like windingscoupled in the coaxial connector, wherein said transmitter includes afrequency generator for generating a carrier signal, and a modulator formodulating signals onto the carrier signal, said signals to betransmitted to the receiver, said receiver including a demodulator forrestoring signals by demodulation, wherein said modulator modulateselectric signals for a plurality of receivers onto said same carriersignal, wherein the receivers are located in a door of said vehicle, thetransmitter is located elsewhere in the automobile and in the area wherethe door is rotatably affixed to the automobile frame with hinges, onepart of the coaxial connector is affixed to the door and another part ofthe coaxial connector is affixed to the automobile body, the coaxialconnector has two parts, wherein the two parts of the coaxial connectorare penetrating each other the way the two parts of a door hingepenetrate each other.
 15. The apparatus as set forth in claim 14,wherein the coaxial connector is a hinge.
 16. The apparatus as set forthin claim 15, wherein the receivers are located in an automobile door,the transmitter is located elsewhere in the automobile and, in the areawhere the door is rotably affixed to the automobile frame with hinges,one part of the coaxial connector is affixed to the door and anotherpart of the coaxial connector is affixed to the automobile body.
 17. Theapparatus as set forth in claim 14, wherein the coaxial connector is atransformer having a primary and secondary winding whose primary windingis affixed to the automobile body exterior and whose secondary windingis affixed to the door and encloses a ferromagnetic hinge pin whichprojects into a ferromagnetic yoke said yoke is affixed to theautomobile body.
 18. The apparatus as set forth in claim 17, wherein thehinge pin consists of a longitudinally slotted tube made fromnon-magnetic steel with a soft magnetic core.
 19. The apparatus as setforth in claim 14, wherein a bus control equipment is provided for thesupply of several electric power consuming devices in the door withelectric control signals and for the supply of another power consumingdevice, such as a loud speaker with low frequency audio signals, andthat the bus control equipment contains an inquiry unit forinterrogating the position of one of the switches and other operatingelements located exterior to the door and a microprocessor forcontrolling the sequence of operations in the bus control equipment,whereby the modulator receives the low frequency signals and modulatesthem onto the carrier signal and receives control signals from theinquiry unit and modulates them onto the carrier signal in serial dataform and that the demodulator located in the door receives signals fromthe bus control equipment, demodulates them and separates them intocontrol signals and low frequency signals.
 20. An apparatus for thetransmission of low current electric signals through cables of a vehiclefrom a transmitter to a receiver located within said vehicle by means oftwo-wire circuits, which said circuits contain at least one coaxialconnector for separating said transmitter from said receiver, saidtwo-wire circuits closed by transformer-like windings coupled in thecoaxial connector, wherein said transmitter includes a frequencygenerator for generating a carrier signal to the receiver and amodulator for modulating signals onto the carrier signal, said receiverincluding a demodulator for restoring signals by demodulation, whereinsaid modulator modulates electric signals for a plurality of receiversonto said same carrier signal, and the transmitter includes a buscontrol equipment for supplying the receiver with signals and amicroprocessor for the control of a sequence of operations in the buscontrol equipment so that the modulator modulates the signals in serialdata form onto the carrier signal for transmission by means of thetwo-wire circuit through the coaxial connector, wherein the bus controlequipment provides power consuming devices in the door with electriccontrol signals and supplies another power consuming device such as aloud speaker with low frequency audio signals, the bus control equipmentcontaining an inquiry unit for interrogating the position of one ofswitches and other operating elements located exterior to the door and amicroprocessor for controlling the sequence of operations in the buscontrol equipment, whereby the modulator receives the low frequencysignals and modulates them onto the carrier signal and receives controlsignals from the inquiry unit and modulates them onto the carrier signalin serial data form, and the demodulator located in the door receivessignals from the bus control equipment, demodulates them and separatesthem into control signals and low frequency signals.
 21. The apparatusas set forth in claim 20, wherein the demodulator in the door is a partof a door module circuit, said door module circuit also containing a lowfrequency amplifier for the low frequency signals and switching unitsfor converting control signals into corrective action signals.
 22. Theapparatus as set forth in claim 21, wherein the door module is a microcontroller provided for evaluating the demodulated control signals andfor controlling switching units.
 23. The apparatus as set forth in claim20, wherein the bus control equipment is connected with several doormodules.
 24. The apparatus as set forth in claim 23, wherein the doormodule also includes an inquiry unit which interrogates the position ofswitches and other operating elements located in the door, and also amodulator for modulating control signals received from the inquiry unitonto the carrier signal, and wherein in the bus control equipment, ademodulator unit is provided in which the modulated signal transmittedfrom the coaxial connector and the door module is demodulated in orderto restore the control signals, wherein the microprocessor transmits thesignal to switching units for converting the control signals for use incorrective action elements exterior to the doors, and to the modulatorfor transmission to another door module.
 25. A door hinge swivel jointhaving a first and second half, said joint used for the wirelesstransmission of electric signals and electrical currents, said swiveljoint configured as a transformer, whose primary winding is part of onehalf of the hinge and whose secondary winding is part of the other halfof the hinge.